1. Field of the Invention
This invention relates to a method of forming a wiring material with a wiring pattern on the surface of an insulating substrate and, particularly, to a method of forming a wiring material with a wiring pattern, which contains CNT (carbon nanotube) mixed in a metal material, on the surface of an insulating substrate.
2. Description of the Related Art
A carbon nanotube (herein referred to as CNT) is a material that has an excellent electric conductivity, thermal conductivity, and mechanical properties. Therefore, it is used for various applications. One of the applications is a wiring material that a wiring pattern made of a metal material is formed on the surface of an insulating substrate.
It is tried that CNT is mixed into a metal material for the wiring material so as to enhance a resistance to electromigration and an electric conductivity to decrease the line width of a wiring pattern. For that purpose, the CNT has to be uniformly dispersed in the metal material to compose the wiring pattern. The electromigration means a phenomenon that an electron to flow through a wiring collides with a wiring metal atom, thereby the metal atom moves, causing a disconnection of the wiring.
Japanese patent application laid-open No. 2004-156074 discloses a method of uniformly mixing CNT into a metal material, where a dispersion agent and CNT is added into a metal plating solution, thereby the CNT is dispersed by the dispersion agent the metal plating solution, and the metal plating is conducted such that a metal plating film with CNT mixed uniformly therein is formed on the surface of a substrate. The dispersion agent used is cationic and/or anionic surfactant(s).
However, in the above method, since the metal plating film obtained is the dispersion agent exists at the interface of CNT and the metal material, the interface resistance between the CNT and the metal material must increase and, therefore, the electric conductivity cannot be enhanced as expected.